Studies On The Production Of Active Peptides From Cod Fish Skin Fermentation By Aspergillus Oryzae

In this paper, the effects of cod fish skin fermentation by Aspergillus oryzae on releasing active peptide was investigated. The optimization of koji of Aspergillus oryzae, determination of liquid state fermentation medium, optimization of fermentation process to produce peptide and the characteristics of the fermentation peptides were also analysized. This work may provide primary data for further study on the fish skin by products, as well as provide a new way for exploiting to prepare active peptide.The main contents and results of this study were as follows:1. The optimization of Koji of Aspergillus oryzae. Koji of Aspergillus oryzae 3.801 was optimized with the main index of spores by orthogonal test with the sum of 1.25×10¹⁰ per gram mouldstarter in optimum conditions, the most simple fermentation medium was determined with the aim of induction of fermentation cost by auxotroph test, it was proved that 0.1% of MgSO₄ and 0.1% of K₂HPO₄ should be added in the medium to support the growth of Aspergillus oryzae.2. The optimization of fermentation condition of Aspergillus oryzae. The carbon and nitrogen ratio, liquid volume, substrate concentration, ratation speed, carbon, surfactants, different initial pH, inoculation rate were studied and the carbon and nitrogen ratio, inoculum, substrate concentration were chosen as the the most important factor to do the response surface experiment. The optimum fermentation conditions was as follows: 0.29 ratio of carbon and nitrogen, 7.0% substrate concentration, inoculum size 4×10⁷/g .Under the optimum conditions, the degree of hydrolysis of fish skin was 36.7%, and the availability of the model was proved.3. Research on the fermentation peptide in the characteristic of food processing and bioactivity. The peptide included 8 kinds of necessary amino acid and the peptide of which molecular weight below 1000Da took part 70% of all the fermentation peptide. The solubility of the peptide was detected, and the peptide had the lowest solubility at pH 4.0. The foamability, emulsibility and emulsion stability index of the peptide at 1% protein concentration was 61.4%, 72.07 m²/g and 0.451 respectively, indicating the good emulsifying and foaming properties of the peptide. This paper also monitored the activity of antioxidation as well as antihypertense of the peptides, which proved that the rate of DPPH could be 63%, and the IC50 of anti-ACE of peptides was 2.53 mg/ml.4. Analysis of the fermentation process. The process was studied after the ratio of carbon and nitrogen was adjusted to 1:1 which was more symbolistic. HPLC was used to analyse the organic acid and the results indicated that citric acid was the main acid. The content of citric acid increased at first then decreased in the course of fermentation. After the carbon source was run out, the protease activity and the degree of hydrolysis (DH) increased greatly. The protease in the fermentation fluid was isolated and purified by Sephadex G-15, Q-Sepharose FF and Sephadex G-15. The result showed that the protease was neutral protease with molecular weights about 19 kDa.5. Feasibility analysis. Through careful analysis and research, the thesis shows that the project is feasible for that it can recover the cost and bring considerable profits financially and socially.